/* 7zCrc.c -- CRC32 calculation
   2009-11-23 : Igor Pavlov : Public domain */

#include "Types.h"
#include "7zCrc.h"
#include "CpuArch.h"

#define kCrcPoly 0xEDB88320

#ifdef MY_CPU_LE
    #define CRC_NUM_TABLES 8
#else
    #define CRC_NUM_TABLES 1
#endif

typedef UInt32 (MY_FAST_CALL * CRC_FUNC)(UInt32 v, const void* data, size_t size, const UInt32* table);

static CRC_FUNC g_CrcUpdate;
UInt32 g_CrcTable[256 * CRC_NUM_TABLES];

#if CRC_NUM_TABLES == 1

    #define CRC_UPDATE_BYTE_2(crc, b) (table[((crc) ^ (b)) & 0xFF] ^ ((crc) >> 8))

static UInt32 MY_FAST_CALL CrcUpdateT1(UInt32 v, const void* data, size_t size, const UInt32* table)
{
    const Byte* p = (const Byte*)data;
    for (; size > 0; size--, p++)
        v = CRC_UPDATE_BYTE_2(v, *p);
    return v;
}

#else

UInt32 MY_FAST_CALL CrcUpdateT4(UInt32 v, const void* data, size_t size, const UInt32* table);
UInt32 MY_FAST_CALL CrcUpdateT8(UInt32 v, const void* data, size_t size, const UInt32* table);

#endif

UInt32 MY_FAST_CALL CrcUpdate(UInt32 v, const void* data, size_t size)
{
    return g_CrcUpdate(v, data, size, g_CrcTable);
}

UInt32 MY_FAST_CALL CrcCalc(const void* data, size_t size)
{
    return g_CrcUpdate(CRC_INIT_VAL, data, size, g_CrcTable) ^ CRC_INIT_VAL;
}

void MY_FAST_CALL CrcGenerateTable()
{
    UInt32 i;
    for (i = 0; i < 256; i++)
    {
        UInt32 r = i;
        unsigned j;
        for (j = 0; j < 8; j++)
            r = (r >> 1) ^ (kCrcPoly & ~((r & 1) - 1));
        g_CrcTable[i] = r;
    }
    #if CRC_NUM_TABLES == 1
    g_CrcUpdate = CrcUpdateT1;
    #else
    for (; i < 256 * CRC_NUM_TABLES; i++)
    {
        UInt32 r = g_CrcTable[i - 256];
        g_CrcTable[i] = g_CrcTable[r & 0xFF] ^ (r >> 8);
    }
    g_CrcUpdate = CrcUpdateT4;
    #ifdef MY_CPU_X86_OR_AMD64
    if (!CPU_Is_InOrder())
        g_CrcUpdate = CrcUpdateT8;
    #endif
    #endif
}